1. Field of Invention
This invention relates to the field of telecommunications. More specifically, this invention relates to dedicated paging channels that may be used to provide walkie-talkie calls in a telecommunications system.
2. Background
Society is more mobile today than it has ever been before. In response to our increased mobility, technology has had to respond to our ever increasing need to communicate with business colleagues, family members and friends while we are on the move. Thus, mobile communications systems, including wireless telephones and other wireless communications devices have evolved from novel accessories to almost absolute necessities.
An exemplary mobile communications system 100 is depicted in FIG. 1. During typical operation of such a system, the mobile units 125 are communicating with a base station 120 and remain in an idle mode when not engaged in or checking for an active call. Notifications of incoming calls and other traffic are sent from the base station controller 115 to the base station 120 then to the target mobile unit 125 over a paging channel. Thus, one of the most important things mobile unit 125 does while in idle mode is awaken, turn on its receiver and check to see if it has an incoming call or other information from the base station 120 to which it must respond.
The receiver consumes quite a lot of power. Therefore, in an effort to conserve battery life, mobile unit 125 will supply power to its receiver only during active call states or specified monitoring periods referred to as slot cycles. Slot cycles are determined by a slot cycle index associated with mobile unit 125. These slot cycles are initially determined when mobile unit 125 first registers with base station 120. Base station controller 115 and base station 120 determine the paging channel which the mobile unit's receiver will monitor for incoming notifications.
In cdma2000 based systems, slot cycles are typically set at intervals of either 2.56 seconds or 5.12 seconds. This information is passed from the base station to mobiles in the same geographical area. When a call is initiated, the communication system 100 generates the sound of a ringer back to the caller and sends a call notification to the mobile unit 125 of the call recipient. The mobile unit 125 monitors the paging channel for call notifications only during the assigned 80 ms paging channel slots. When the mobile unit 125 receives a call notification, it sends an acknowledgment to the base station. Once the mobile unit 125 acknowledges the notification, the call will be set-up. The call set-up time is determined from the time the caller initiated a call to the time the call recipient answered. This approach is adequate for normal cellular calls and saves battery life since the receiver is not in constant use, but the approach has a disadvantage of longer set-up times.
As explained above, the typical delay for notifying mobile unit 125 of a call is 2.56 seconds or 5.12 seconds. This is without considering the added delay that has incurred due the network side of the operation. Under normal conditions, the 2.56 second or 5.12 second delay is acceptable since the cellular user does not expect immediate response. Currently, however, there are dual service mobile units that are capable of receiving both cellular type calls and walkie-talkie calls. Walkie-talkie calls are of the type where only one person is able to speak at a time. In other words, communications are exchanged in a half-duplex, as opposed to full-duplex mode. Heretofore, one paging channel has been used to provide notification of both regular cellular calls and walkie-talkie calls. Consequently, both types of calls are subject to the same 2.56 second or 5.12 second delay.
Cellular callers do not expect instant connection type of a service, so a few seconds of call set-up time is acceptable. However, it has been found that such delay is unacceptable for walkie-talkie calls. When placing walkie-talkie calls, callers want to connect instantly to those being called. Therefore, what is needed is a technique for providing notification of cellular calls and walkie-talkie calls which reduces the amount of setup time associated with making and receiving walkie-talkie calls.